Three-phase LLC resonant converter

Abstract

The utility model discloses a three-phase LLC resonant converter. The converter is composed of a first-phase LLC resonant converter, a second-phase LLC resonant converter and a third-phase LLC resonant converter which are connected in sequence. And the input end of the first-phase LLC resonant converter is connected in series with the input ends of the second-phase LLC resonant converter and the third-phase LLC resonant converter to form a common input end. The output end of the first-phase LLC resonant converter, the output end of the second-phase LLC resonant converter and the output end of the third-phase LLC resonant converter are connected in parallel to form a common output end. The phase difference between any two resonant converters in the three-phase LLC resonant converter is 120 degrees. And the first-phase LLC resonant converter, the second-phase LLC resonant converter and the third-phase LLC resonant converter share one magnetic integrated transformer. Each of the first-phase LLC resonant converter, the second-phase LLC resonant converter and the third-phase LLC resonant converter is provided with two resonant circuits. According to the invention, the conduction loss of the three-phase LLC resonant converter can be reduced.

Description

Technical Field

[0001] The present application relates to the field of semiconductor technology, and in particular to a three-phase LLC resonant converter. Background Art

[0002] With the development of communication technology, server applications are becoming more and more extensive, so the demand for power is also increasing. In order to meet this demand, the server power system uses a distributed architecture and uses an intermediate bus converter (Inverted Buck-Boost Converter, IBC) to achieve DC voltage conversion and isolation. In IBC, the LLC resonant converter (LL-C Resonant Converter) is one of the most suitable topologies because it can fix the switching frequency at the resonant frequency point under open-loop conditions, thereby maximizing efficiency. However, most resonant converters have some problems, one of the main problems is conduction loss, especially for the loss of transformers and rectifiers. In low-voltage and high-power applications, the conduction loss of the LLC converter is high, which will increase the heat generation of the device, increase the difficulty of heat dissipation, and reduce the conversion efficiency. Utility Model Content

[0003] Based on the above problems, the present application provides a three-phase LLC resonant converter, which can reduce the conduction loss of the LLC converter, thereby improving the conversion efficiency of the converter.

[0004] The embodiments of the present application disclose the following technical solutions:

[0005] A three-phase LLC resonant converter, the three-phase LLC resonant converter comprising a first-phase LLC resonant converter, a second-phase LLC resonant converter and a third-phase LLC resonant converter connected in sequence;

[0006] The input end of the first-phase LLC resonant converter is connected in series with the input end of the second-phase LLC resonant converter and the input end of the third-phase LLC resonant converter to form a common input end of the three-phase LLC resonant converter; the output end of the first-phase LLC resonant converter, the output end of the second-phase LLC resonant converter and the output end of the third-phase LLC resonant converter are connected in parallel to each other to form a common output end of the three-phase LLC resonant converter; the common input end includes a positive input end and a negative input end; the common output end includes a positive output end and a negative output end;

[0007] The phase difference between any two resonant converters in the three-phase LLC resonant converter is 120 degrees;

[0008] The first-phase LLC resonant converter, the second-phase LLC resonant converter and the third-phase LLC resonant converter share a magnetic integrated transformer;

[0009] The first-phase LLC resonant converter, the second-phase LLC resonant converter, and the third-phase LLC resonant converter each have two resonant circuits.

[0010] In a possible implementation, it is characterized in that:

[0011] Each phase of the LLC resonant converter in the three-phase LLC resonant converter is controlled by a high-frequency pulse width modulation (PWM) signal with a duty cycle of 50%;

[0012] Among them, the high-frequency PWM signal is controlled as a fixed-frequency signal.

[0013] In a possible implementation, it is characterized in that:

[0014] The first-phase LLC resonant converter includes a first input capacitor and a first half-bridge; the second-phase LLC resonant converter includes a second input capacitor and a second half-bridge; the third-phase LLC resonant converter includes a third input capacitor and a third half-bridge;

[0015] The first input terminal of the first half-bridge is connected to the first terminal of the first input capacitor and is connected to the positive input terminal;

[0016] The second input terminal of the first half-bridge is connected to the second terminal of the first input capacitor, and is connected to the first input terminal of the second half-bridge and the first terminal of the second input capacitor;

[0017] The second input terminal of the second half-bridge is connected to the second terminal of the second input capacitor, and is connected to the first input terminal of the third half-bridge and the first terminal of the third input capacitor;

[0018] The second input terminal of the third half bridge is connected to the second terminal of the third input capacitor and is connected to the negative input terminal of the converter.

[0019] In a possible implementation, it is characterized in that:

[0020] The resonant frequency of the first resonant circuit is the same as the resonant frequency of the third resonant circuit and the resonant frequency of the fifth resonant circuit, and all of them are fundamental frequencies;

[0021] The resonant frequency of the second resonant circuit is the same as the resonant frequency of the fourth resonant circuit and the resonant frequency of the sixth resonant circuit, and all of them are third harmonic frequencies;

[0022] The third harmonic frequency is three times the fundamental frequency; and the third harmonic voltage gain corresponding to the third harmonic frequency is the same as the fundamental voltage gain corresponding to the fundamental frequency.

[0023] In a possible implementation, it is characterized in that:

[0024] The first-phase LLC resonant converter further includes a first resonant circuit, a second resonant circuit and the magnetic integrated transformer; the second-phase LLC resonant converter further includes a third resonant circuit, a fourth resonant circuit and the magnetic integrated transformer; the third-phase LLC resonant converter further includes a fifth resonant circuit, a sixth resonant circuit and the magnetic integrated transformer; the first resonant circuit includes a first resonant inductor and a first resonant capacitor connected in sequence; the second resonant circuit includes a second resonant inductor and a second resonant capacitor connected in sequence; the third resonant circuit includes a third resonant inductor and a third resonant capacitor connected in sequence; the fourth resonant circuit includes a fourth resonant inductor and a fourth resonant capacitor connected in sequence; the fifth resonant circuit includes a fifth resonant inductor and a fifth resonant capacitor connected in sequence; the sixth resonant circuit includes a sixth resonant inductor and a sixth resonant capacitor; wherein the second resonant inductor, the fourth resonant inductor and the sixth resonant inductor are all coupled inductors;

[0025] The output end of the first half bridge is connected to the first end of the first resonant inductor and the first end of the second resonant inductor; the output end of the second half bridge is connected to the first end of the third resonant inductor and the first end of the fourth resonant inductor; the output end of the third half bridge is connected to the first end of the fifth resonant inductor and the first end of the sixth resonant inductor;

[0026] The first end of the first resonant capacitor is connected to the second end of the first resonant inductor, and the second end of the first resonant capacitor is connected to the second end of the second resonant capacitor and the third end of the second resonant inductor;

[0027] The first end of the second resonant capacitor is connected to the second end of the second resonant inductor; the first end of the primary side of the magnetic integrated transformer is connected to the fourth end of the second resonant inductor;

[0028] The first end of the third resonant capacitor is connected to the second end of the third resonant inductor, and the second end is connected to the second end of the fourth resonant capacitor and the third end of the fourth resonant inductor;

[0029] The first end of the fourth resonant capacitor is connected to the second end of the fourth resonant inductor; the third end of the primary side of the magnetic integrated transformer is connected to the fourth end of the fourth resonant inductor;

[0030] The first end of the fifth resonant capacitor is connected to the second end of the fifth resonant inductor, and the second end is connected to the second end of the sixth resonant capacitor and the third end of the sixth resonant inductor;

[0031] The first end of the sixth resonant capacitor is connected to the second end of the sixth resonant inductor; the fifth end of the primary side of the magnetic integrated transformer is connected to the fourth end of the sixth resonant inductor;

[0032] The second primary end of the magnetic integrated transformer is connected to the fourth primary end and the sixth primary end.

[0033] In a possible implementation, it is characterized in that:

[0034] The first-phase LLC resonant converter further includes a first rectifier circuit; the second-phase LLC resonant converter further includes a second rectifier circuit; the third-phase LLC resonant converter further includes a third rectifier circuit; the first rectifier circuit, the second rectifier circuit and the third rectifier circuit are all full-bridge circuits;

[0035] The first input end of the first rectifier circuit is connected to the first end of the secondary side of the magnetic integrated transformer, and the second input end of the first rectifier circuit is connected to the second end of the secondary side of the magnetic integrated transformer;

[0036] The first input end of the second rectifier circuit is connected to the third end of the secondary side of the magnetic integrated transformer, and the second input end of the second rectifier circuit is connected to the fourth end of the secondary side of the magnetic integrated transformer;

[0037] The first input end of the third rectifier circuit is connected to the fifth end of the secondary side of the magnetic integrated transformer, and the second input end of the third rectifier circuit is connected to the sixth end of the secondary side of the magnetic integrated transformer;

[0038] The first output end of the first rectifier circuit is also connected to the first output end of the second rectifier circuit and the first output end of the third rectifier circuit respectively, and is connected to the positive output end;

[0039] The second output end of the first rectifier circuit is also connected to the second output end of the second rectifier circuit and the second output end of the third rectifier circuit respectively, and is connected to the negative output end.

[0040] In a possible implementation, it is characterized in that:

[0041] The first half-bridge includes a first power switch tube and a second power switch tube; the first resonant circuit includes a first resonant inductor and a first resonant capacitor; the second half-bridge includes a third power switch tube and a fourth power switch tube; the third half-bridge includes a fifth power switch tube and a sixth power switch tube;

[0042] The drain of the first power switch tube is connected to the first end of the first input capacitor and is connected to the positive input end; the source of the first power switch tube is connected to the drain of the second power switch tube;

[0043] The drain of the third power switch tube is connected to the first end of the second input capacitor, and is connected to the source of the second power switch tube and the second end of the first input capacitor; the source of the third power switch tube is connected to the drain of the fourth power switch tube;

[0044] The drain of the fifth power switch tube is connected to the first end of the third input capacitor, and is connected to the source of the fourth power switch tube and the second end of the second input capacitor; the source of the fifth power switch tube is connected to the drain of the sixth power switch tube;

[0045] The source of the sixth power switch tube is connected to the second end of the third input capacitor and is connected to the negative input end.

[0046] In a possible implementation, it is characterized in that:

[0047] The first rectifier circuit includes a first rectifier tube, a second rectifier tube, a third rectifier tube and a fourth rectifier tube; the second rectifier circuit includes a fifth rectifier tube, a sixth rectifier tube, a seventh rectifier tube and an eighth rectifier tube; the third rectifier circuit includes a ninth rectifier tube, a tenth rectifier tube, an eleventh rectifier tube and a twelfth rectifier tube;

[0048] The first end of the first rectifier is connected to the first end of the third rectifier and connected to the positive output end; the second end of the first rectifier is connected to the first end of the second rectifier and connected to the second end of the secondary side of the magnetic integrated transformer; the second end of the third rectifier is connected to the first end of the fourth rectifier and connected to the first end of the secondary side of the magnetic integrated transformer; the second end of the second rectifier is connected to the second end of the fourth rectifier and connected to the negative output end;

[0049] The first end of the fifth rectifier is connected to the first end of the seventh rectifier and connected to the positive output end; the second end of the fifth rectifier is connected to the first end of the sixth rectifier and connected to the second end of the secondary side of the magnetic integrated transformer; the second end of the seventh rectifier is connected to the first end of the eighth rectifier and connected to the first end of the secondary side of the magnetic integrated transformer; the second end of the sixth rectifier is connected to the second end of the eighth rectifier and connected to the negative output end;

[0050] The first end of the ninth rectifier is connected to the first end of the eleventh rectifier and to the positive output end; the second end of the ninth rectifier is connected to the first end of the tenth rectifier and to the second end of the secondary side of the magnetic integrated transformer; the second end of the eleventh rectifier is connected to the first end of the twelfth rectifier and to the first end of the secondary side of the magnetic integrated transformer; the second end of the tenth rectifier is connected to the second end of the twelfth rectifier and to the negative output end.

[0051] In a possible implementation, it is characterized in that the magnetic integrated transformer includes a first magnetic column, a second magnetic column and a third magnetic column;

[0052] The windings corresponding to the first end and the second end of the primary side of the magnetic integrated transformer are wound clockwise on the first magnetic column; the windings corresponding to the first end and the second end of the secondary side of the magnetic integrated transformer are wound clockwise on the first magnetic column;

[0053] The windings corresponding to the third and fourth primary ends of the magnetic integrated transformer are wound clockwise on the first magnetic column; the windings corresponding to the third and fourth secondary ends of the magnetic integrated transformer are wound clockwise on the first magnetic column;

[0054] The windings corresponding to the fifth and sixth primary ends of the magnetic integrated transformer are wound clockwise on the first magnetic column; the windings corresponding to the fifth and sixth secondary ends of the magnetic integrated transformer are wound clockwise on the first magnetic column.

[0055] In a possible implementation, it is characterized in that:

[0056] The three-phase LLC resonant converter also includes an output capacitor;

[0057] The first end of the output capacitor is connected to the positive output end, and the second end of the output capacitor is connected to the negative output end.

[0058] Compared with the prior art, this application has the following beneficial effects:

[0059] The present application provides a three-phase LLC resonant converter. Specifically, the three-phase LLC resonant converter is formed by connecting three single-phase LLC resonant converters in sequence. Their input ends are connected in series to form a common input end, and their output ends are connected in parallel to form a common output end. The phase difference between any two single-phase LLC resonant converters is 120 degrees. In addition, the three single-phase LLC resonant converters share a magnetic integrated transformer, and each single-phase LLC resonant converter has two resonant circuits. The present application reduces the number of windings and reuses inductive devices by having three single-phase LLC resonant converters share a magnetic integrated transformer and connect them in series with each other, thereby reducing the leakage current and voltage drop of the switch tube and effectively reducing the conduction loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] In order to more clearly illustrate the technical solutions in this embodiment or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0061] Figure 1 A schematic diagram of the structure of a three-phase LLC resonant converter provided in an embodiment of the present application;

[0062] Figure 2 A driving timing diagram of a three-phase LLC resonant converter provided in an embodiment of the present application;

[0063] Figure 3 An equivalent circuit diagram of a resonant circuit provided in an embodiment of the present application;

[0064] Figure 4 A schematic diagram of the magnetic core structure of a magnetically integrated transformer of a three-phase LLC resonant converter provided in an embodiment of the present application. DETAILED DESCRIPTION

[0065] To facilitate understanding of the technical solutions provided by the embodiments of the present application, the background technology involved in the embodiments of the present application will be described below.

[0066] With the development of communication technology, servers are widely used and the demand for power is increasing. Therefore, distributed architecture and IBC are used to achieve DC voltage conversion and isolation. Among them, LLC resonant converter is one of the most suitable topologies because it can fix the switching frequency at the resonant frequency point under open-loop conditions, thereby maximizing efficiency. However, traditional LLC converters have conduction loss problems, especially for the loss of transformers and rectifiers, which will increase the heat generation of devices, increase the difficulty of heat dissipation, and reduce conversion efficiency. This problem is more prominent in low-voltage and high-power applications.

[0067] In order to solve this problem, a three-phase LLC resonant converter is provided in an embodiment of the present application, and the three-phase LLC resonant converter is composed of a first-phase LLC resonant converter, a second-phase LLC resonant converter and a third-phase LLC resonant converter connected in sequence. Among them, the input end of the first-phase LLC resonant converter is connected in series with the input end of the second-phase LLC resonant converter and the input end of the third-phase LLC resonant converter, forming a common input end of the positive input end and the negative input end. The output end of the first-phase LLC resonant converter, the output end of the second-phase LLC resonant converter and the output end of the third-phase LLC resonant converter are connected in parallel to each other, forming a common output end including a positive output end and a negative output end. The phase difference between any two resonant converters is 120 degrees. In addition, three single-phase LLC resonant converters share a magnetic integrated transformer, and each single-phase LLC resonant converter has two resonant circuits. The conduction loss of the three-phase LLC resonant converter of the present application is low.

[0068] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0069] See also Figure 1 , Figure 1 A schematic diagram of the structure of a three-phase LLC resonant converter provided in an embodiment of the present application is shown in FIG. Figure 1 As shown, the three-phase LLC resonant converter includes: a first-phase LLC resonant converter, a second-phase LLC resonant converter and a third-phase LLC resonant converter.

[0070] The three-phase LLC resonant converter adopts an input series and output parallel structure, that is, the input end of the first-phase LLC resonant converter is connected in series with the input end of the second-phase LLC resonant converter and the input end of the third-phase LLC resonant converter to form a common input end. The output end of the first-phase LLC resonant converter, the output end of the second-phase LLC resonant converter and the output end of the third-phase LLC resonant converter are connected in parallel to form a common output end.

[0071] The first-phase LLC resonant converter includes: a first input capacitor C1; a first half-bridge, the first half-bridge includes a first power switch tube Q1 and a second power switch tube Q2; a first resonant circuit, the first resonant circuit includes a first resonant inductor Lr1 and a first resonant capacitor Cr1; a second resonant circuit, the second resonant circuit includes a second resonant inductor Lr2 and a second resonant capacitor Cr2; a magnetic integrated transformer T; and a first rectifier circuit.

[0072] The second-phase LLC resonant converter includes: a second input capacitor C2; a second half-bridge, the second half-bridge includes a third power switch tube Q3 and a fourth power switch tube Q4; a third resonant circuit, the third resonant circuit includes a third resonant inductor Lr3 and a third resonant capacitor Cr3; a fourth resonant circuit, the fourth resonant circuit includes a fourth resonant inductor Lr4 and a fourth resonant capacitor Cr4; a magnetic integrated transformer T; a second rectifier circuit, the second rectifier circuit includes a fifth rectifier tube D5, a sixth rectifier tube D6, a seventh rectifier tube D7, and an eighth rectifier tube D8.

[0073] The third-phase LLC resonant converter includes: a third input capacitor C3; a third half-bridge, the third half-bridge includes a fifth power switch tube Q5 and a sixth power switch tube Q6; a fifth resonant circuit, the fifth resonant circuit includes a fifth resonant inductor Lr5 and a fifth resonant capacitor Cr5; a sixth resonant circuit, the sixth resonant circuit includes a sixth resonant inductor L6 and a sixth resonant capacitor Cr6; a magnetic integrated transformer T; a third rectifier circuit, the third rectifier circuit includes a ninth rectifier tube D9, a tenth rectifier tube D10, an eleventh rectifier tube D11, and a twelfth rectifier tube D12.

[0074] The first input end of the first half bridge is connected to the first end of the first input capacitor C1, and is connected to the positive input end of the converter; the second input end of the first half bridge is connected to the second end of the first input capacitor C1, and is connected to the first input end of the second half bridge and the first end of the second input capacitor C2; the second input end of the second half bridge is connected to the second end of the second input capacitor C2, and is connected to the first input end of the third half bridge and the first end of the third input capacitor C3; the second input end of the third half bridge is connected to the second end of the third input capacitor C3, and is connected to the negative input end of the converter.

[0075] The output end of the first half bridge is connected to the first end of the first resonant inductor Lr1 and the first end of the second resonant inductor Lr2; the output end of the second half bridge is connected to the first end of the third resonant inductor Lr3 and the first end of the fourth resonant inductor Lr4; the output end of the third half bridge is connected to the first end of the fifth resonant inductor Lr5 and the first end of the sixth resonant inductor L6.

[0076] The first end of the first resonant capacitor Cr1 is connected to the second end of the first resonant inductor Lr1, the second end of the first resonant capacitor Cr1 is connected to the second end of the second resonant capacitor Cr2 and the third end of the second resonant inductor Lr2; the first end of the second resonant capacitor Cr2 is connected to the second end of the second resonant inductor Lr2, and the primary first end A of the magnetic integrated transformer T is connected to the fourth end of the second resonant inductor Lr2;

[0077] The first end of the third resonant capacitor Cr3 is connected to the second end of the third resonant inductor Lr3, the second end of the third resonant capacitor Cr3 is connected to the second end of the fourth resonant capacitor Cr4 and the third end of the fourth resonant inductor Lr4; the first end of the fourth resonant capacitor Cr4 is connected to the second end of the fourth resonant inductor Lr4, and the third end of the primary side of the magnetic integrated transformer T is connected to the fourth end of the fourth resonant inductor Lr4;

[0078] The first end of the fifth resonant capacitor Cr5 is connected to the second end of the fifth resonant inductor Lr5, the second end of the fifth resonant capacitor Cr5 is connected to the second end of the sixth resonant capacitor Cr6 and the third end of the sixth resonant inductor L6; the first end of the sixth resonant capacitor Cr6 is connected to the second end of the sixth resonant inductor L6, and the fifth end E of the primary side of the magnetic integrated transformer T is connected to the fourth end of the sixth resonant inductor L6;

[0079] The second primary terminal B of the magnetic integrated transformer T is connected to the fourth primary terminal D and the sixth primary terminal F.

[0080] The first rectifier circuit, the second rectifier circuit and the third rectifier circuit are full-bridge circuits.

[0081] The first input end of the first rectifier circuit is connected to the first end U of the secondary side of the magnetic integrated transformer T, and the second input end of the first rectifier circuit is connected to the second end V of the secondary side of the magnetic integrated transformer T; the first input end of the second rectifier circuit is connected to the third end W of the secondary side of the magnetic integrated transformer T, and the second input end of the second rectifier circuit is connected to the fourth end X of the secondary side of the magnetic integrated transformer T; the first input end of the third rectifier circuit is connected to the fifth end Y of the secondary side of the magnetic integrated transformer T, and the second input end of the third rectifier circuit is connected to the sixth end Z of the secondary side of the magnetic integrated transformer T; the first output end of the first rectifier circuit is connected to the first output end of the second rectifier circuit and the first output end of the third rectifier circuit, and is connected to the positive output end of the converter; the second output end of the first rectifier circuit is connected to the second output end of the second rectifier circuit and the second output end of the third rectifier circuit, and is connected to the negative output end of the converter.

[0082] In a possible implementation, the first half-bridge includes a first power switch tube Q1 and a second power switch tube Q2; the first resonant circuit includes a first resonant inductor Lr1 and a first resonant capacitor Cr1; the second half-bridge includes a third power switch tube Q3 and a fourth power switch tube Q4; the third half-bridge includes a fifth power switch tube Q5 and a sixth power switch tube Q6.

[0083] The drain of the first power switch tube Q1 is connected to the first end of the first input capacitor C1 and is connected to the positive input end; the source of the first power switch tube Q1 is connected to the drain of the second power switch tube Q2;

[0084] The drain of the third power switch tube Q3 is connected to the first end of the second input capacitor C2, and is connected to the source of the second power switch tube Q2 and the second end of the first input capacitor C1; the source of the third power switch tube Q3 is connected to the drain of the fourth power switch tube Q4;

[0085] The drain of the fifth power switch tube Q5 is connected to the first end of the third input capacitor C3, and is connected to the source of the fourth power switch tube Q4 and the second end of the second input capacitor C2; the source of the fifth power switch tube Q5 is connected to the drain of the sixth power switch tube Q6;

[0086] The source of the sixth power switch tube Q6 is connected to the second end of the third input capacitor C3 and is also connected to the negative input end.

[0087] It should be noted that the gate of each power switch tube is usually connected to an input terminal in the driving circuit, and a certain signal voltage is applied to the gate through the input terminal to control the conduction and cutoff of the power switch tube. Specifically, according to different types of power switch tubes such as P-type and N-type, the gate needs to be connected to different signal voltages.

[0088] In a possible implementation, the first rectifier circuit includes a first rectifier tube D1, a second rectifier tube D2, a third rectifier tube D3 and a fourth rectifier tube D4; the second rectifier circuit includes a fifth rectifier tube D5, a sixth rectifier tube D6, a seventh rectifier tube D7 and an eighth rectifier tube D8; the third rectifier circuit includes a ninth rectifier tube D9, a tenth rectifier tube D10, an eleventh rectifier tube D11 and a twelfth rectifier tube D12;

[0089] The first end of the first rectifier tube D1 is connected to the first end of the third rectifier tube D3, and is connected to the positive output end; the second end of the first rectifier tube D1 is connected to the first end of the second rectifier tube D2, and is connected to the second end V of the secondary side of the magnetic integrated transformer T; the second end of the third rectifier tube D3 is connected to the first end of the fourth rectifier tube D4, and is connected to the first end U of the secondary side of the magnetic integrated transformer T; the second end of the second rectifier tube D2 is connected to the second end of the fourth rectifier tube D4, and is connected to the negative output end;

[0090] The first end of the fifth rectifier tube D5 is connected to the first end of the seventh rectifier tube D7, and is connected to the positive output end; the second end of the fifth rectifier tube D5 is connected to the first end of the sixth rectifier tube D6, and is connected to the secondary second end V of the magnetic integrated transformer T; the second end of the seventh rectifier tube D7 is connected to the first end of the eighth rectifier tube D8, and is connected to the secondary first end U of the magnetic integrated transformer T; the second end of the sixth rectifier tube D6 is connected to the second end of the eighth rectifier tube D8, and is connected to the negative output end;

[0091] The first end of the ninth rectifier D9 is connected to the first end of the eleventh rectifier D11, and is connected to the positive output end; the second end of the ninth rectifier D9 is connected to the first end of the tenth rectifier D10, and is connected to the second end V of the secondary side of the magnetic integrated transformer T; the second end of the eleventh rectifier D11 is connected to the first end of the twelfth rectifier D10, and is connected to the first end V of the secondary side of the magnetic integrated transformer T; the second end of the tenth rectifier D10 is connected to the second end of the twelfth rectifier D12, and is connected to the negative output end.

[0092] See also Figure 2 , Figure 2 A driving timing diagram of a three-phase LLC resonant converter provided in an embodiment of the present application, Figure 2 The six curves from top to bottom are the drive signal conversion curves of the first power switch tube Q1, the second power switch tube Q2, the third power switch tube Q3, the fourth power switch tube Q4, the fifth power switch tube Q5, and the sixth power switch tube Q6. The three-phase LLC resonant converter is controlled by a high-frequency pulse width modulation (PWM) signal with a 50% duty cycle. The drive signals of the upper and lower tubes of each half-bridge are complementary, and the phase difference between each phase is 120 degrees. The time waveforms of the three-phase PWM signals have a phase difference of 120 degrees from each other, so that the alternating conduction and cutoff of each branch in the three-phase circuit can be realized. Due to the superposition of the output currents of each phase, the ripple current of the output capacitor is reduced, and the size of the output capacitor can be reduced.

[0093] At the same time, the high-frequency PWM signal control of the three-phase LLC resonant converter is a fixed-frequency signal. With fixed-frequency control, the converter operates at the fundamental resonant frequency point, and its voltage conversion ratio is constant and independent of the load, achieving high conversion efficiency.

[0094] exist Figure 2 In the PWM, dead time refers to the fact that it takes a certain amount of time for the power switch to turn on and off. In order to prevent two different power switches from turning on at the same time and causing a short circuit, a short delay time is added between two adjacent PWM pulses to prevent the on-time of the two switches from overlapping. This delay time is called dead time.

[0095] Specifically, when a PWM signal finishes outputting a high level and starts outputting a low level, a certain dead time must pass before the two power switches are turned off to avoid problems such as short circuits or staggered on and off.

[0096] The length of the dead time depends on factors such as the drive circuit design and the response time of the power switch tube. Generally, a smaller dead time can improve the conversion efficiency of the entire circuit, but it will also increase the switching loss and EMI interference of the power switch tube. Therefore, it is necessary to balance factors such as dead time, conversion efficiency and power switch tube loss during design.

[0097] It should be noted that the two resonant circuits of each phase LLC resonant converter are resonant, so there are two resonant frequencies. When calculating the resonant frequency of the resonant circuit, the two resonant circuits need to be converted into an equivalent circuit for calculation. Figure 3 , Figure 3 A resonant circuit equivalent circuit diagram provided in an embodiment of the present application, if Figure 3 is the equivalent circuit of the first resonant circuit and the second resonant circuit, then Figure 3 Where Leq1 is the equivalent resonant inductance of the first resonant circuit, Ceq1 is the equivalent resonant capacitance of the first resonant circuit, Leq2 is the equivalent resonant inductance of the second resonant circuit, Ceq2 is the equivalent resonant capacitance of the second resonant circuit, Lm is the transformer equivalent magnetizing inductance, Rload is the equivalent load resistance, and the input Vin of the equivalent circuit is the output of the first half bridge; if Figure 3 is the equivalent circuit of the third resonant circuit and the fourth resonant circuit, then Figure 3 Where Leq1 is the equivalent resonant inductance of the third resonant circuit, Ceq1 is the equivalent resonant capacitance of the third resonant circuit, Leq2 is the equivalent resonant inductance of the fourth resonant circuit, Ceq2 is the equivalent resonant capacitance of the fourth resonant circuit, Lm is the transformer equivalent magnetizing inductance, Rload is the equivalent load resistance, and the input Vin of the equivalent circuit is the output of the second half bridge; if Figure 3 is the equivalent circuit of the fifth resonant circuit and the sixth resonant circuit, then Figure 3 Leq1 is the equivalent resonant inductance of the fifth resonant circuit, Ceq1 is the equivalent resonant capacitance of the fifth resonant circuit, Leq2 is the equivalent resonant inductance of the sixth resonant circuit, Ceq2 is the equivalent resonant capacitance of the sixth resonant circuit, Lm is the equivalent magnetizing inductance of the transformer, Rload is the equivalent load resistance, and the input Vin of the equivalent circuit is the output of the third half bridge.

[0098] The resonant frequency of the first resonant circuit is the same as the resonant frequency of the third resonant circuit and the resonant frequency of the fifth resonant circuit, which is the fundamental frequency.

[0099] The resonant frequency of the second resonant circuit is the same as the resonant frequency of the fourth resonant circuit and the resonant frequency of the sixth resonant circuit, which is the third harmonic frequency.

[0100] Among them, the third harmonic frequency is 3 times the fundamental frequency, fr3 =3*f r1 .

[0101] The use of third harmonic frequency can optimize the LLC resonant current waveform and greatly reduce the peak value and effective value of the secondary current.

[0102] The resonant circuit can be equivalent to a bandpass filter. According to Fourier decomposition, the symmetrical periodic square wave can be decomposed into the sum of a set of simple oscillation functions. The impedance of the first resonant circuit is zero at the resonant frequency, so the fundamental wave is not affected. The impedance of the second resonant circuit is zero at the third harmonic frequency, so the third harmonic is not affected. For other harmonics, the resonant circuit impedance is large, so other high-order harmonic components in the resonant circuit are eliminated. Injecting the third harmonic through the second resonant circuit can reduce the conduction loss. The third harmonic voltage gain is the same as the fundamental voltage gain, and the third harmonic current is injected into the total current, which greatly reduces the peak value and effective value of the secondary current.

[0103] The second resonant inductor Lr2, the fourth resonant inductor Lr4 and the sixth resonant inductor Lr6 are coupled inductors, and negative inductance is constructed by the coupled inductors to offset each other with the transformer leakage inductance, so as to eliminate the influence of the transformer leakage inductance on the resonant circuit.

[0104] See also Figure 4 , Figure 4 A schematic diagram of the magnetic core structure of a magnetic integrated transformer of a three-phase LLC resonant converter provided in an embodiment of the present application;

[0105] The magnetic integrated transformer is composed of a single EI type magnetic core, including a first magnetic column, a second magnetic column and a third magnetic column.

[0106] The windings corresponding to the primary first end A and the primary second end B of the magnetic integrated transformer are wound clockwise on the first magnetic column; the windings corresponding to the secondary first end U and the secondary second end V of the magnetic integrated transformer are wound clockwise on the first magnetic column;

[0107] The windings corresponding to the third terminal C and the fourth terminal D of the primary side of the magnetic integrated transformer are wound clockwise on the first magnetic column; the windings corresponding to the third terminal W and the fourth terminal X of the secondary side of the magnetic integrated transformer are wound clockwise on the first magnetic column;

[0108] The windings corresponding to the fifth primary terminal E and the sixth primary terminal F of the magnetic integrated transformer are wound clockwise on the first magnetic column; the windings corresponding to the fifth secondary terminal Y and the sixth secondary terminal Z of the magnetic integrated transformer are wound clockwise on the first magnetic column.

[0109] In a possible implementation, the three-phase LLC resonant converter further includes an output capacitor C4.

[0110] A first terminal of the output capacitor C4 is connected to the positive output terminal, and a second terminal of the output capacitor C4 is connected to the negative output terminal.

[0111] Optionally, the output capacitor C4 can be an electrolytic capacitor with positive and negative poles, or a non-polar capacitor. When the output capacitor C4 is an electrolytic capacitor with positive and negative poles, the positive pole of the output capacitor C4 is connected to the positive output terminal, and the negative pole of the output capacitor C4 is connected to the negative output terminal.

[0112] The above is a detailed introduction to a three-phase LLC resonant converter provided by the present application. The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same and similar parts between the various embodiments can refer to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can refer to the method part description. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present application, several improvements and modifications can be made to the present application, and these improvements and modifications also fall within the scope of protection of the claims of the present application.

[0113] It should be understood that in the present application, "at least one (item)" means one or more, and "plurality" means two or more. "And / or" is used to describe the association relationship of associated objects, indicating that three relationships may exist. For example, "A and / or B" can mean: only A exists, only B exists, and A and B exist at the same time, where A and B can be singular or plural. The character " / " generally indicates that the objects associated before and after are in an "or" relationship. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, at least one of a, b or c can mean: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, c can be single or multiple.

Claims

1. A three-phase LLC resonant converter, characterized in that: The three-phase LLC resonant converter comprises a first-phase LLC resonant converter, a second-phase LLC resonant converter and a third-phase LLC resonant converter which are connected in sequence; The input end of the first-phase LLC resonant converter is connected in series with the input end of the second-phase LLC resonant converter and the input end of the third-phase LLC resonant converter to form a common input end of the three-phase LLC resonant converter; the output end of the first-phase LLC resonant converter, the output end of the second-phase LLC resonant converter and the output end of the third-phase LLC resonant converter are connected in parallel to each other to form a common output end of the three-phase LLC resonant converter; the common input end includes a positive input end and a negative input end; the common output end includes a positive output end and a negative output end; The phase difference between any two resonant converters in the three-phase LLC resonant converter is 120 degrees; The first-phase LLC resonant converter, the second-phase LLC resonant converter and the third-phase LLC resonant converter share a magnetic integrated transformer; The first-phase LLC resonant converter, the second-phase LLC resonant converter, and the third-phase LLC resonant converter each have two resonant circuits.

2. The three-phase LLC resonant converter according to claim 1, characterized in that: Each phase of the LLC resonant converter in the three-phase LLC resonant converter is controlled by a high-frequency pulse width modulation PWM signal with a duty cycle of 50%; Among them, the high-frequency PWM signal is controlled as a fixed-frequency signal.

3. The three-phase LLC resonant converter according to claim 1, characterized in that: The first-phase LLC resonant converter includes a first input capacitor and a first half-bridge; the second-phase LLC resonant converter includes a second input capacitor and a second half-bridge; The third-phase LLC resonant converter includes a third input capacitor and a third half-bridge; The first input terminal of the first half-bridge is connected to the first terminal of the first input capacitor and is connected to the positive input terminal; The second input terminal of the first half-bridge is connected to the second terminal of the first input capacitor, and is connected to the first input terminal of the second half-bridge and the first terminal of the second input capacitor; The second input terminal of the second half-bridge is connected to the second terminal of the second input capacitor, and is connected to the first input terminal of the third half-bridge and the first terminal of the third input capacitor; The second input terminal of the third half bridge is connected to the second end of the third input capacitor and is connected to the negative input terminal of the converter.

4. The three-phase LLC resonant converter according to claim 3, characterized in that: The resonant frequency of the first resonant circuit is the same as the resonant frequency of the third resonant circuit and the resonant frequency of the fifth resonant circuit, and all of them are fundamental frequencies; The resonant frequency of the second resonant circuit is the same as the resonant frequency of the fourth resonant circuit and the resonant frequency of the sixth resonant circuit, and all of them are third harmonic frequencies; The third harmonic frequency is three times the fundamental frequency; and the third harmonic voltage gain corresponding to the third harmonic frequency is the same as the fundamental voltage gain corresponding to the fundamental frequency.

5. The three-phase LLC resonant converter according to claim 3, characterized in that: The first-phase LLC resonant converter further includes a first resonant circuit, a second resonant circuit and the magnetic integrated transformer; the second-phase LLC resonant converter further includes a third resonant circuit, a fourth resonant circuit and the magnetic integrated transformer; the third-phase LLC resonant converter further includes a fifth resonant circuit, a sixth resonant circuit and the magnetic integrated transformer; the first resonant circuit includes a first resonant inductor and a first resonant capacitor connected in sequence; the second resonant circuit includes a second resonant inductor and a second resonant capacitor connected in sequence; the third resonant circuit includes a third resonant inductor and a third resonant capacitor connected in sequence; the fourth resonant circuit includes a fourth resonant inductor and a fourth resonant capacitor connected in sequence; the fifth resonant circuit includes a fifth resonant inductor and a fifth resonant capacitor connected in sequence; the sixth resonant circuit includes a sixth resonant inductor and a sixth resonant capacitor; wherein the second resonant inductor, the fourth resonant inductor and the sixth resonant inductor are all coupled inductors; The output end of the first half bridge is connected to the first end of the first resonant inductor and the first end of the second resonant inductor; the output end of the second half bridge is connected to the first end of the third resonant inductor and the first end of the fourth resonant inductor; the output end of the third half bridge is connected to the first end of the fifth resonant inductor and the first end of the sixth resonant inductor; The first end of the first resonant capacitor is connected to the second end of the first resonant inductor, and the second end of the first resonant capacitor is connected to the second end of the second resonant capacitor and the third end of the second resonant inductor; The first end of the second resonant capacitor is connected to the second end of the second resonant inductor; the first end of the primary side of the magnetic integrated transformer is connected to the fourth end of the second resonant inductor; The first end of the third resonant capacitor is connected to the second end of the third resonant inductor, and the second end is connected to the second end of the fourth resonant capacitor and the third end of the fourth resonant inductor; The first end of the fourth resonant capacitor is connected to the second end of the fourth resonant inductor; the third end of the primary side of the magnetic integrated transformer is connected to the fourth end of the fourth resonant inductor; The first end of the fifth resonant capacitor is connected to the second end of the fifth resonant inductor, and the second end is connected to the second end of the sixth resonant capacitor and the third end of the sixth resonant inductor; The first end of the sixth resonant capacitor is connected to the second end of the sixth resonant inductor; the fifth end of the primary side of the magnetic integrated transformer is connected to the fourth end of the sixth resonant inductor; The second primary end of the magnetic integrated transformer is connected to the fourth primary end and the sixth primary end.

6. The three-phase LLC resonant converter according to claim 3, characterized in that: The first-phase LLC resonant converter further includes a first rectifier circuit; the second-phase LLC resonant converter further includes a second rectifier circuit; the third-phase LLC resonant converter further includes a third rectifier circuit; the first rectifier circuit, the second rectifier circuit and the third rectifier circuit are all full-bridge circuits; The first input end of the first rectifier circuit is connected to the first end of the secondary side of the magnetic integrated transformer, and the second input end of the first rectifier circuit is connected to the second end of the secondary side of the magnetic integrated transformer; The first input end of the second rectifier circuit is connected to the third end of the secondary side of the magnetic integrated transformer, and the second input end of the second rectifier circuit is connected to the fourth end of the secondary side of the magnetic integrated transformer; The first input end of the third rectifier circuit is connected to the fifth end of the secondary side of the magnetic integrated transformer, and the second input end of the third rectifier circuit is connected to the sixth end of the secondary side of the magnetic integrated transformer; The first output end of the first rectifier circuit is also connected to the first output end of the second rectifier circuit and the first output end of the third rectifier circuit respectively, and is connected to the positive output end; The second output end of the first rectifier circuit is also connected to the second output end of the second rectifier circuit and the second output end of the third rectifier circuit respectively, and is connected to the negative output end.

7. The three-phase LLC resonant converter according to claim 3, characterized in that: The first half-bridge includes a first power switch tube and a second power switch tube; the first resonant circuit includes a first resonant inductor and a first resonant capacitor; the second half-bridge includes a third power switch tube and a fourth power switch tube; the third half-bridge includes a fifth power switch tube and a sixth power switch tube; The drain of the first power switch tube is connected to the first end of the first input capacitor and is connected to the positive input end; the source of the first power switch tube is connected to the drain of the second power switch tube; The drain of the third power switch tube is connected to the first end of the second input capacitor, and is connected to the source of the second power switch tube and the second end of the first input capacitor; The source of the third power switch tube is connected to the drain of the fourth power switch tube; The drain of the fifth power switch tube is connected to the first end of the third input capacitor, and is connected to the source of the fourth power switch tube and the second end of the second input capacitor; The source of the fifth power switch tube is connected to the drain of the sixth power switch tube; The source of the sixth power switch tube is connected to the second end of the third input capacitor and is connected to the negative input end.

8. The three-phase LLC resonant converter according to claim 6, characterized in that: The first rectifier circuit includes a first rectifier tube, a second rectifier tube, a third rectifier tube and a fourth rectifier tube; the second rectifier circuit includes a fifth rectifier tube, a sixth rectifier tube, a seventh rectifier tube and an eighth rectifier tube; the third rectifier circuit includes a ninth rectifier tube, a tenth rectifier tube, an eleventh rectifier tube and a twelfth rectifier tube; The first end of the first rectifier is connected to the first end of the third rectifier and connected to the positive output end; the second end of the first rectifier is connected to the first end of the second rectifier and connected to the second end of the secondary side of the magnetic integrated transformer; the second end of the third rectifier is connected to the first end of the fourth rectifier and connected to the first end of the secondary side of the magnetic integrated transformer; the second end of the second rectifier is connected to the second end of the fourth rectifier and connected to the negative output end; The first end of the fifth rectifier is connected to the first end of the seventh rectifier and connected to the positive output end; the second end of the fifth rectifier is connected to the first end of the sixth rectifier and connected to the second end of the secondary side of the magnetic integrated transformer; the second end of the seventh rectifier is connected to the first end of the eighth rectifier and connected to the first end of the secondary side of the magnetic integrated transformer; the second end of the sixth rectifier is connected to the second end of the eighth rectifier and connected to the negative output end; The first end of the ninth rectifier is connected to the first end of the eleventh rectifier and to the positive output end; the second end of the ninth rectifier is connected to the first end of the tenth rectifier and to the second end of the secondary side of the magnetic integrated transformer; the second end of the eleventh rectifier is connected to the first end of the twelfth rectifier and to the first end of the secondary side of the magnetic integrated transformer; the second end of the tenth rectifier is connected to the second end of the twelfth rectifier and to the negative output end.

9. The three-phase LLC resonant converter according to claim 1, characterized in that: The magnetic integrated transformer comprises a first magnetic column, a second magnetic column and a third magnetic column; The windings corresponding to the first end and the second end of the primary side of the magnetic integrated transformer are wound clockwise on the first magnetic column; the windings corresponding to the first end and the second end of the secondary side of the magnetic integrated transformer are wound clockwise on the first magnetic column; The windings corresponding to the third and fourth primary ends of the magnetic integrated transformer are wound clockwise on the first magnetic column; the windings corresponding to the third and fourth secondary ends of the magnetic integrated transformer are wound clockwise on the first magnetic column; The windings corresponding to the fifth and sixth primary ends of the magnetic integrated transformer are wound clockwise on the first magnetic column; the windings corresponding to the fifth and sixth secondary ends of the magnetic integrated transformer are wound clockwise on the first magnetic column.

10. The three-phase LLC resonant converter according to claim 1, characterized in that: The three-phase LLC resonant converter also includes an output capacitor; The first end of the output capacitor is connected to the positive output end, and the second end of the output capacitor is connected to the negative output end.

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